The present invention relates to a method of cleaning the inside of a coil pipe(s) of a heat exchanger and, more specifically, to a method of cleaning the inside of the cooling coil pipe(s) or heating coil pipe(s) of the heat exchanger by forcing water and ice to flow in the coil pipe(s) for removing off dirt deposits such as slime, sludge and residue.
As well known, a heat exchanger transfers heat from a heat transfer medium (e.g., water or steam) passing through in a coil pipe(s) to other medium (e.g., air or water) flowing along the outside of the coil pipe(s) to cool or heat the latter. Dirt deposited in the coil pipe(s) results in a decrease in working efficiency of the heat exchanger. For example, the decreased cooling or heating ability of air conditioners is resulted in most cases from dirt deposits in the cooling or heating coil pipe(s). Namely, the dirt deposited in the coil pipe(s) may prevent the heat exchange between the heating or cooling medium flowing therein and the air flowing along the outside of the coil pipe(s). The buildup of slime, sludge and residue in the coil pipe(s) may also reduce the passage of heat transfer medium (cold or hot water in case of air conditioner) in the coil pipe(s), resulting in lowering the flow rate of the medium flowing therein than the nominal value necessary for achieving designed temperature difference between two fluids cannot be achieved.
For example, a cooling coil pipe(s) or heating coil pipe(s) of a heat exchanger (for chilled or hot water) of an air conditioner may be severely fouled in 10-15 years' use. This results in lowered cooling or heating capacity and shortening the service life of the device. To recover the capacity of the air conditioner, it is usually conducted to increase the airflow rate, wash the fin side (air side) of the heat exchanger coil pipe(s) with high-pressure water and, in rare cases, clean the inside of the heat exchanger coil pipe(s) (heat transfer side) with cleaning agent.
As described above, a heat exchanger coil pipe(s) is usually cleaned by washing its outside wall (air side) and, in rare cases, by flushing its inside wall (water side) with chemical solution. With regard to waste piping, the present applicant has proposed washing the inside of waste pipes with ice cubes in Japanese Patent Publication No. 1-28625.
However, the use of cleaning chemicals is accompanied by a risk of corroding the inside wall of the heat exchanger coil pipe(s) and polluting the environment with waste solution containing residue of chemicals. Therefore, there has been desired a method of cleaning the inside of heat exchanger coil pipe(s), which is friendly both to the heat exchanger coil pipe(s) and the ecological environment. The present invention is directed to a cleaning method that can satisfy the above-described requirements.